Nitrogen inputs and irrigation frequency influence population dynamics of Mesocriconema xenoplax under grapevines

Nitrogen fertilization and irrigation are critical for tree fruit and grape production in semi-arid regions of Western North America. Growers are increasingly considering more conservative fertilization and irrigation practices in order to optimize fruit quality while minimizing environmental impacts. The implications of such shifts in production practices for pest populations are not well known and need to be considered. Plant-parasitic nematodes are soil-dwelling microscopic roundworms that are pests of many types of crops including grapevines. The ring nematode, Mesocriconema xenoplax, which is known to be a significant pest of grapes, was recently been found to be widespread in Okanagan vineyards. This study was conducted to determine if the frequency of drip irrigation frequency (daily vs approximately every third day) and nitrogen fertilizer rates (ranging from 0 to 64 kg N/ha/year) affect the buildup of ring nematode populations in vineyards. The eight combinations of irrigation and fertilization treatments were initiated in 2006 in a planting of ‘Merlot’ wine-grapes in the central Okanagan Valley, and applied annually thereafter. Nematode populations in root zone soil were then assessed in spring, summer and fall of 2010 and 2011. The researchers found that ring nematode population densities increased with nitrogen fertilization rate under the daily irrigation regime but not under the low frequency irrigation regime. These results suggest that reductions in nitrogen fertilization rates and irrigation frequency, that have environmental benefits and minimal impacts on fruit quality and yield, can also minimize the buildup of populations of the pesky ring nematode, M. xenoplax.